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Expedition 3 Trial

Achaia Taltoan, Mercer University College of Pharmacy

Alzheimer’s disease (AD) involves the development of extracellular amyloid beta (Aβ) plaques and intracellular fibrous tangles of tau protein. [1] The Aβ hypothesis postulates that overproduction or reduced clearance of Aβ from the cerebrum leads to formation of Aβ plaques, resulting in the cognitive deficits of Alzheimer’s disease. [1] Solanezumab is a humanized G1 monoclonal antibody that binds to Aβ peptides to increase clearance from the brain.[2] The Expedition and Expedition 2 trials evaluated the use of solanezumab in mild to moderate Alzheimer’s disease; pooled secondary analyses demonstrated a significant improvement in functional and cognitive decline in mild Alzheimer’s disease patients.[3] The Expedition 3 trial seeks to clarify the findings of the previous Expedition trials through limiting the population to mild Alzheimer’s disease patients.

Patients were randomized to receive intravenous solanezumab 400mg or placebo every four weeks for 76 weeks. Patients maintained acetylcholinesterase inhibitors, memantine, and other non-pharmacological treatments for AD concomitantly with study medications. The patients were administered the Alzheimer’s Disease Assessment Scale-Cognitive subscale (ADAS-cog14) and Alzheimer’s Disease Cooperative Study-Instrumental Activities of Daily Living (ADCS-iADL) 12, 28 40,52, 64, and 80 weeks after baseline; as well as the Mini-Mental State Examination (MMSE), the Functional Activities Questionnaire (FAQ), and the Clinical Dementia Rating Scale-Sum of Boxes (CDR-SB). The CDR-SB was administered only at baseline and final study visit. Plasma Aβ1-40 and Aβ1-42 levels, CSF samples, and Florbetapir PET scans were taken at baseline, and genetic testing for the APOEε4 genotype was collected in patients where allowed by law. Patients who completed the treatment period could progress to an open arm extension study. Follow up period was six months with telephone or mail contact. Analyses were conducted based on the intention to treat principle. Fisher’s exact test and Pearson’s chi-square test was used for trial group comparisons of categorical data. Secondary outcomes were not analyzed for statistical significance.

Duration

July 2013-February 2017 (date retrieved from clinicaltrials.gov)

Primary Outcome Measure

The change in score on the 14-item cognitive subscale of the Alzheimer’s Disease Assessment Scale (ADAS-cog14) from baseline to 80 weeks

The primary outcomes were changed before the study was executed from ADAS-Cog14 and ADCS-iADL to the ADAS-Cog14 alone. [4] The ADAS-Cog14 primarily assesses cognitive function while the ADCS-iADL evaluates the functional ability of dementia patients. [5] This appears to be a rational decision because recent evidence suggests cognitive decline precedes functional decline in dementia patients. [6] It would have been beneficial to assess the CSF levels of solanezumab to evaluate whether enough drug penetrated the blood brain barrier to affect the Ab concentrations. Overall, this trial does not support the use of solanezumab 400 mg in mild dementia patients.